The Celts had been little more than a jumble of many different tribes before the Romans came. The Romans had ruled England and the south of Scotland as a single country. But when they left it the Celts had let it fall to pieces again. The Norsemen tried, time after time, to make one United Kingdom; but they never quite succeeded for more than a few years. They had to wait for the empire-building Normans to teach them how to make, first, a kingdom and then an empire that would last. Yet Offa, Edgar, and Canute went far towards making the first step by trying to raise a Royal Navy strong enough to command at least the English sea. Offa, king of Mercia or Middle England (757-796) had no sooner fought his way outwards to a sure foothold on the coast than he began building a fleet so strong that even the great Emperor Charlemagne, though ruling the half of Europe, treated him on equal terms. Here is Offa's good advice to all future kings of England: "He who would be safe on land must be supreme at sea." Alfred the Great (871-901) was more likely to have been thinking of the navy than of anything else when, as a young man hiding from the Danes, he forgot to turn the cakes which the housewife had left him to watch. Anyhow he tried the true way to stop the Danes, by attacking them before they landed, and he caused ships of a new and better kind to be built for the fleet. Edgar (959-975) used to go round Great Britain every year inspecting the three different fleets into which his navy was divided; one off the east of England, another off the north of Scotland, and the third in the Irish Sea. It is said that he was once rowed at Chester on the River Dee by no less than eight kings, which showed that he was following Offa's advice by making his navy supreme over all the neighbouring coasts of England, Ireland, Scotland, and Wales. After Edgar's death the Danes held command of the sea. They formed the last fierce wave of hardy Norsemen to break in fury on the English shore and leave descendants who are seamen to the present day. Nelson, greatest of all naval commanders, came from Norfolk, where Danish blood is strongest. Most of the fishermen on the east coast of Great Britain are of partly Danish descent; and no one served more faithfully through the Great War than these men did against the submarines and mines. King George V, whose mother is a Dane, and who is himself a first-rate seaman, must have felt a thrill of ancestral pride in pinning V.C.'s over their undaunted hearts. Fifty years before the Norman conquest Canute the Dane became sole king of England. He had been chosen King of Denmark by the Danish Fleet. But he was true to England as well; and in 1028, when he conquered Norway, he had fifty English vessels with him.